<template>
  <div class="xtx-infinite-loading" ref="target">
    <div class="loading" v-if="loading">
      <span class="img"></span>
      <span class="text">正在加载...</span>
    </div>
    <div class="none" v-if="finished">
      <span class="img"></span>
      <span class="text">{{ finishedText }}</span>
    </div>
  </div>
</template>

<script>
import { ref, onMounted, onBeforeUnmount, watch } from 'vue'
export default {
  name: 'XtxPullLoad',
  props: {
    loading: {
      type: Boolean,
      default: false
    },
    finished: {
      type: Boolean,
      default: false
    },
    'finished-text': {
      type: String,
      default: '亲，没有更多了'
    }
  },
  setup (props, { emit }) {
    const target = ref(null)
    let io

    watch(
      () => props.loading,
      newVal => {
        if (!props.loading && !props.finished) {
          io = new IntersectionObserver(
            function ([{ isIntersecting }]) {
              if (isIntersecting) {
                console.log('进入可视区')

                if (!props.loading && !props.finished) {
                  emit('onload')
                  io && io.observe(target.value)
                }
              }
            },
            { threshold: [0] }
          )
        }
      },
      { immediate: true }
    )
    watch(
      () => props.finished,
      newVal => {
        if (newVal) {
          io && io.observe(target.value)
        }
      }
    )

    onMounted(() => {
      io && io.observe(target.value)
    })

    onBeforeUnmount(() => {
      console.log('销毁')
      io && io.disconnect()
    })

    return { target }
  }
}
</script>

<style scoped lang="less">
.xtx-infinite-loading {
  .loading {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 200px;
    .img {
      width: 50px;
      height: 50px;
      background: url(../../assets/images/load.gif) no-repeat center / contain;
    }
    .text {
      color: #999;
      font-size: 16px;
    }
  }
  .none {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 200px;
    .img {
      width: 200px;
      height: 134px;
      background: url(../../assets/images/none.png) no-repeat center / contain;
    }
    .text {
      color: #999;
      font-size: 16px;
    }
  }
}
</style>
